The goal of this proposal is to determine the role of pH regulation and membrane conductance in fuel-stimulated insulin secretion from Beta-cells. These studies will be carried out on insulinoma cells from transplantable tumors and from clonal lines and from normal cultured Beta-cells from rat islets, which differ in their secretory response characteristics. Specifically, our goals will be (1) to elucidate the molecular mechanism(s) of regulation of intracellular pH, (2) to identify and characterize ionic membrane channels and (3) to test the hypothesis that stimulation of insulin released is mediated by alterations in intracellular pH and/or membrane conductance. These results will be closely correlated with secretion, bioenergetics and Ca++ homeostasis studies in these same cells through collaboration with members of the Diabetes Center.